This specification relates to information retrieval.
Conventional online travel booking sites allow users to identify and purchase travel according to a specified itinerary. For example, a user may use a flight search tool to view flight itineraries that match flight search parameters such as origin location, destination location, and travel dates. The user can select and purchase a flight itinerary that best matches the user's preferences. Typically, following the purchase of a particular flight itinerary, the user will follow the flight itinerary and complete the trip.